Fuel cells with improved resistance to fuel crossover

Abstract

The invention provides a fuel cell comprising an anode in an anode region of the cell and a cathode in a cathode region of the cell, the anode being separated from the cathode by an ion selective polymer electrolyte membrane, the anode region of the cell being supplied in use thereof with an alcoholic fuel, the cathode region of the cell being supplied in use thereof with an oxidant, the cell being provided with means for generating an electrical circuit between the anode and the cathode and with a non-volatile redox couple in solution in flowing fluid communication with the cathode in the cathode region of the cell, the redox couple being at least partially reduced at the cathode in operation of the cell, and at least partially regenerated by reaction with the oxidant after such reduction at the cathode.

What is claimed is: 
     
         1 . A fuel cell comprising an anode in an anode region of the cell and a cathode in a cathode region of the cell, the anode being separated from the cathode by an ion selective polymer electrolyte membrane, the anode region of the cell being supplied with an alcoholic fuel, the cathode region of the cell being supplied with an oxidant, the cell being provided with means for generating an electrical circuit between the anode and the cathode and with a non-volatile redox couple in solution in flowing fluid communication with the cathode in the cathode region of the cell, the redox couple being at least partially reduced at the cathode in operation of the cell, and at least partially re-generated by reaction with the oxidant after such reduction at the cathode, the redox potential of the redox couple being from 0.01V to 0.6V different from the potential of oxygen and the redox couple and/or the concentration of the redox couple in the catholyte solution being selected so that the current density generated by the cell in operation is substantially unaffected by the oxidation of alcoholic fuel due to crossover of the alcoholic fuel from the anode region of the cell to the cathode region of the cell across the polymer electrolyte membrane. 
     
     
         2 . A fuel cell according to  claim 1  wherein the alcoholic fuel is selected from methanol, ethanol, propanol, isopropanol and butanol, dipropylene glycol and ethylene glycol, and mixtures of two or more thereof. 
     
     
         3 . A fuel cell according to  claim 1  wherein the redox potential of the redox couple is from 0.01V to 0.3V different from the potential of oxygen. 
     
     
         4 . A fuel cell according to  claim 1  wherein the operating temperature of the fuel cell is below 100° C. 
     
     
         5 . A fuel cell according to  claim 1  wherein the redox couple comprises at least one transition metal complex. 
     
     
         6 . A fuel cell according to  claim 5  wherein the redox couple comprises a polyoxometallate species. 
     
     
         7 . A fuel cell according to  claim 1  wherein the concentration of the redox couple in the catholyte solution is at least about 0.1M. 
     
     
         8 . A fuel cell according to  claim 1  wherein the cathode region of the cell is provided with a reservoir for storing the catholyte solution. 
     
     
         9 . A fuel cell according to  claim 1  wherein the fuel cell is fitted with a switchable electronic valve to allow reverse flow of electrons along the connecting line when electromotive force is supplied to the fuel cell.